OpenVPN on Ubuntu 18.04

I needed to install Ubuntu 18.04 recently and I ran into some problems with OpenVPN 2.4.4 not working (it had worked fine with OpenVPN 2.4.0 from Debian stretch/stable). The errors pointed to ns-cert-type being the problem, which is indeed a deprecated option. But that led me to find suggestions to instead use remote-cert-tls server that did not help me get things working.

Rather, the problem ended up being with these options that I’m sometimes required to add to get openvpn working:

up /etc/openvpn/update-resolv-conf
down /etc/openvpn/update-resolv-conf

Following the advice from this answer in the Ubuntu forums, I had to make just a few tweaks to get things working.

First, install openvpn-systemd-resolved:

sudo apt install openvpn-systemd-resolved

Second, add these four lines (yes, with script-security 2) at the end of client.ovpn: